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United States Patent | 5,182,153 |
Miyake ,   et al. | January 26, 1993 |
A magnetic disc comprising a nonmagnetic substrate made of a synthetic resin film and at least one magnetic layer on the surface of the substrate has improved reliability when it having a dimensional shrinkage factor of not more than 0.04% in a radial direction after keeping the magnetic disc at 60.degree. C., 90% RH for 64 hours and then keeping it at room temperature for 72 hours.
Inventors: | Miyake; Akira (Mishima, JP); Yamamoto; Yoshinori (Takatsuki, JP) |
Assignee: | Hitachi Maxell, Ltd. (Osaka, JP) |
Appl. No.: | 376509 |
Filed: | July 7, 1989 |
Jul 13, 1988[JP] | 63-174635 |
Current U.S. Class: | 428/847.2; 204/192.2; 427/129; 428/323; 428/423.7; 428/480; 428/900 |
Intern'l Class: | G11B 023/00; B05D 005/12; C23C 014/00; B32B 003/02 |
Field of Search: | 428/480,694,900,64,65,323,423.7 427/129 204/192.2 |
4270412 | Jun., 1981 | Katoh et al. | 428/480. |
4275107 | Jun., 1981 | Bartkus et al. | 428/220. |
4481231 | Nov., 1984 | Hashimoto et al. | 427/128. |
4652479 | Mar., 1987 | Suzuki et al. | 428/64. |
4680197 | Jul., 1987 | Sagoi et al. | 204/192. |
4728577 | Mar., 1988 | Yamada et al. | 428/480. |
4780353 | Oct., 1988 | Takahashi et al. | 428/480. |
4801481 | Jan., 1989 | Sagoi et al. | 428/64. |
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______________________________________ Component Parts ______________________________________ Co-containing .gamma.-Fe.sub.2 O.sub.3 100 Nitrocellulose resin 15.6 (HC 100 manufactured by Daicel) Polyurethane resin 15.6 (HI 2000 manufactured by Dainippon Ink) .alpha.-Al.sub.2 O.sub.3 (average particle size, 0.4 .mu.m) 10 Oleyl oleate 10 Butylcellosolve stearate 1 Cyclohexanone 140 Toluene 140 ______________________________________
TABLE ______________________________________ Example Degree of Heat Heat shrinkage Decrease of No. shrinkage (.mu.m) factor (%) output (dB) ______________________________________ 1 20 0.015 -0.5 2 35 0.027 -0.9 3 30 0.023 -0.7 Comp. 1 180 0.138 -5.6 Comp. 2 220 0.170 -7.5 ______________________________________